This invention relates in general to the construction of valves and in particular to a new and useful symmetrically arranged valve which comprises a single rotary valve piston and a housing having a central fluid passage and a double rotary piston valve arrangement below and with a portion on each side of the central fluid passage.
In a prior art pneumatic jigging machine for upgrading coal or preparing other minerals, where additional strokes are super-imposed on basic strokes (German Pat. No. 26 54 593), comprising one or more water filled washing compartments including a jig bed for the material to be prepared and one or more air chambers which are provided at the side of, or below, the jig bed and are exposable to pulses of compressed air, which air chambers communicate, through air lines having air inlets and air outlets and through interposed control devices (rotary piston slide valves), to an air tank, the rotary piston slide valves for basic strokes, and for additional strokes, are provided between the air tank and the jigging machine in tandem arrangement, considered in the longitudinal direction of the machine.
In such a design, the two air lines are angled below the rotary piston slide valve and extend toward the center where they are united to a single line. A relatively large space is needed if two rotary piston slide valves and their associated lines are to be provided for each of the washing compartments.